- Author: Alejandro Del Pozo-Valdivia
It has been a couple of “rough” weeks managing the diamondback moth (DBM), Plutella xylostella (Lepidoptera: Plutellidae), in the Central Coast. Based on my conversations with some PCAs, we are managing large populations of this moth, resulting in high infestations in cole crops like broccoli and Brussel sprouts. Larvae of this insect will typically feed on the underside of the leaves, rasping the epidermis and generating this characteristic “window panning” that results on perforations later on (Fig. 1). Diamondback larvae will also feed on the plant's growing points, floral stalks, and even on flower buds.
It seems like populations have been building up during early summer in our area, resulting in enough individuals, at this point, generating significant injury in cole crops. PCAs have been recommending spraying several different insecticides to reduce the infesting populations in affected fields, since damage has been beyond tolerable. For instance, after one of my field visits, I was able to spot affected larvae in treated fields (Fig. 2). Treatments are working, I believe we need to continue being ahead of future DMB infestations.
Some information to consider:
- Scout early. If you have transplants or direct seeded seedlings, pay a visit more often. We are dealing with a large DBM population right now. There will be a high chance that those fields may ended having DMB earlier than expected during this time of the year.
- Use of adjuvants. The waxy nature of cole crop leaves represents a challenge for insecticide deposition in the canopy. Make sure that you are using a spreader/sticker adjuvant to potentially reduce any pesticide “sliding off” from the waxy leaves.
- Rotate pesticides. Consider using different classes of insecticides, before using different active ingredients within the same class. For instance, using an avermectin and then a diamide, instead of using chlorantraniliprole and cyantraniliprole (two different active ingredients within the diamide class) back to back. Using different modes of actions will help to delay potential issues of developing insecticide resistance in our DBM populations.
- Author: Stephanie Parreira
Celebrate National Honey Bee Day by brushing up on your knowledge of bee protection—check out the newly revised Best Management Practices to Protect Bees from Pesticides and Bee Precaution Pesticide Ratings from UC IPM. These resources will help you strike the right balance between applying pesticides to protect crops and reducing the risk of harming our most important pollinators.
The best management practices now contain important information regarding the use of adjuvants and tank mixes, preventing the movement of pesticide-contaminated dust, and adjusting chemigation practices to reduce bee exposure to pesticide-contaminated water. The Bee Precaution Pesticide Ratings have also been updated to include ratings for 38 new pesticides, including insecticides (baits, mixtures, and biological active ingredients), molluscicides (for snail and slug control), and fungicides.
Most tree and row crops are finished blooming by now, but it is a good idea to learn about bee protection year-round. Visit these resources today to choose pesticides that are least toxic to bees and learn how you can help prevent bees from being harmed by pesticide applications.